Pretty sure the tractor (and likely the grapple) would have been a sunk cost given the intended uses for the property (as originally described) and given seeding 35 acres would run pretty close to $2k (at 50lbs/acre) I'd question if hiring it out, and starting with bare earth would actually have been a cheaper option even if it'd have been faster (depending on local backlogs). That's of course assuming the 10k is a valid estimate for the amount of work that needed to be done - which may or may not be valid for the OP's area.
I know in my area landscapers and clearing crews have gotten pretty ridiculously (by my standards) priced. For example: 2k-4k+ estimates for removal of shrubs and a couple dozen trees in the beds around a house -- all of which was removed by myself (with a tractor) and coworker (with a chainsaw), and mulched with a rented
chipper in under 16 hours of work.
In fact it's bad enough, that if it wasn't for me actually enjoying my work (most of the time), and my disinclination to put up with the types of personalities that I know exist in the local area I'd be very tempted to walk away from my (reasonably well paying) engineering job and start a small clearing/landscaping/treecare outfit. It seems that (around here) anything fast will be excessively expensive, anything reasonably priced will likely take months (and lots of phone calls) to get done, and anything in-between will be expensive --and the price isn't always reflective of the quality of work.
All of which has driven me to the conclusion that in my current locality there's not much that I can't do faster, cheaper and of equal -or in some cases better- quality by either buying or renting the necessary equipment myself. Which I suspect is likely due to an excessive number of white-collar workers who can't/won't do such things themselves and are more than willing to pay whatever price to have someone else do it for them.
So as you said to each their own, and based upon what I've seen/heard around my part of the country I'd add each really needs to investigate the options/costs for their own area.